The invention relates to a device and a method for pulse width modulation.
Modulation is the change of signal parameters of a carrier as a function of a signal to be modulated (base band signal).
Demodulation is a further modulation process that serves to retrieve the base band signal.
In a typical configuration of a communication system, a correspondingly modulated signal (modulation product) is generated by a modulator provided at a corresponding terminal by modulation from a carrier and a signal—originating from a source—to be modulated. This modulated signal is, via a communication channel, transmitted to a demodulator provided at a further terminal.
The demodulator transmits a signal generated from the modulated signal by demodulation—i.e. the retrieved base band signal—to a drain provided at the further terminal.
Alternatively, both a source and a drain each may be provided at the terminal and the further terminal; such terminals then include both a modulator and a demodulator, or a modem (modulator/demodulator), respectively.
As a carrier for the modulation, appropriate sinusoidal oscillations (sinusoidal carriers) may be used, or—to an increasing degree—pulse carriers.
In the case of sinusoidal carriers, the following signal parameters may be influenced for modulation: amplitude, frequency, zero phase, etc., and in the case of pulse carriers the signal parameters pulse amplitude, pulse frequency, pulse phase, pulse duration (pulse width).
Pulse duration or pulse width modulation methods (PDM or PWM methods) are used in entertainment electronics, e.g., for the modulation of audio and video signals.
Conventional digital pulse width modulators require a relatively high temporal resolution of the pulse widths, which necessitates e.g., a clock frequency of approx. 100 MHz in the case of audio signals in the range of 0 to 20 kHz.
A known method for digital pulse width modulation is described in Jorge Varona, ECE University of Toronto: “Power Digital to Analog Conversion Using Sigma Delta and Pulse Width Modulations”.
A disadvantage is in particular the relatively high circuitry effort.
DE 10350336.6, U.S. Ser. No. 10/976,074, Infineon Technologies, inventor: Ch. Braun, describes a pulse width modulation method in which a pulse width modulated signal is used as a feedback signal in a digital loop, and is thus linearized.
With a corresponding pulse width modulated signal, a class-D amplifier may be triggered. The power consumption of a class-D amplifier is higher, the higher the pulse frequency of the pulse width modulated signal.
For this reason, the pulse frequency of the pulse width modulated signal should be as low as possible.
Conventionally, low pulse frequencies can be realized with a relatively high circuitry effort only.
For these and other reasons, there is a need for the present invention.